Imported Debian version 2.5.3~trusty1
[deb_ffmpeg.git] / ffmpeg / libavcodec / rangecoder.h
1 /*
2 * Range coder
3 * Copyright (c) 2004 Michael Niedermayer <michaelni@gmx.at>
4 *
5 * This file is part of FFmpeg.
6 *
7 * FFmpeg is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU Lesser General Public
9 * License as published by the Free Software Foundation; either
10 * version 2.1 of the License, or (at your option) any later version.
11 *
12 * FFmpeg is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 * Lesser General Public License for more details.
16 *
17 * You should have received a copy of the GNU Lesser General Public
18 * License along with FFmpeg; if not, write to the Free Software
19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20 */
21
22 /**
23 * @file
24 * Range coder.
25 */
26
27 #ifndef AVCODEC_RANGECODER_H
28 #define AVCODEC_RANGECODER_H
29
30 #include <stdint.h>
31
32 #include "libavutil/common.h"
33 #include "libavutil/avassert.h"
34
35 typedef struct RangeCoder {
36 int low;
37 int range;
38 int outstanding_count;
39 int outstanding_byte;
40 uint8_t zero_state[256];
41 uint8_t one_state[256];
42 uint8_t *bytestream_start;
43 uint8_t *bytestream;
44 uint8_t *bytestream_end;
45 } RangeCoder;
46
47 void ff_init_range_encoder(RangeCoder *c, uint8_t *buf, int buf_size);
48 void ff_init_range_decoder(RangeCoder *c, const uint8_t *buf, int buf_size);
49 int ff_rac_terminate(RangeCoder *c);
50 void ff_build_rac_states(RangeCoder *c, int factor, int max_p);
51
52 static inline void renorm_encoder(RangeCoder *c)
53 {
54 // FIXME: optimize
55 while (c->range < 0x100) {
56 if (c->outstanding_byte < 0) {
57 c->outstanding_byte = c->low >> 8;
58 } else if (c->low <= 0xFF00) {
59 *c->bytestream++ = c->outstanding_byte;
60 for (; c->outstanding_count; c->outstanding_count--)
61 *c->bytestream++ = 0xFF;
62 c->outstanding_byte = c->low >> 8;
63 } else if (c->low >= 0x10000) {
64 *c->bytestream++ = c->outstanding_byte + 1;
65 for (; c->outstanding_count; c->outstanding_count--)
66 *c->bytestream++ = 0x00;
67 c->outstanding_byte = (c->low >> 8) & 0xFF;
68 } else {
69 c->outstanding_count++;
70 }
71
72 c->low = (c->low & 0xFF) << 8;
73 c->range <<= 8;
74 }
75 }
76
77 static inline int get_rac_count(RangeCoder *c)
78 {
79 int x = c->bytestream - c->bytestream_start + c->outstanding_count;
80 if (c->outstanding_byte >= 0)
81 x++;
82 return 8 * x - av_log2(c->range);
83 }
84
85 static inline void put_rac(RangeCoder *c, uint8_t *const state, int bit)
86 {
87 int range1 = (c->range * (*state)) >> 8;
88
89 av_assert2(*state);
90 av_assert2(range1 < c->range);
91 av_assert2(range1 > 0);
92 if (!bit) {
93 c->range -= range1;
94 *state = c->zero_state[*state];
95 } else {
96 c->low += c->range - range1;
97 c->range = range1;
98 *state = c->one_state[*state];
99 }
100
101 renorm_encoder(c);
102 }
103
104 static inline void refill(RangeCoder *c)
105 {
106 if (c->range < 0x100) {
107 c->range <<= 8;
108 c->low <<= 8;
109 if (c->bytestream < c->bytestream_end)
110 c->low += c->bytestream[0];
111 c->bytestream++;
112 }
113 }
114
115 static inline int get_rac(RangeCoder *c, uint8_t *const state)
116 {
117 int range1 = (c->range * (*state)) >> 8;
118
119 c->range -= range1;
120 #if 1
121 if (c->low < c->range) {
122 *state = c->zero_state[*state];
123 refill(c);
124 return 0;
125 } else {
126 c->low -= c->range;
127 *state = c->one_state[*state];
128 c->range = range1;
129 refill(c);
130 return 1;
131 }
132 #else
133 {
134 int one_mask one_mask = (c->range - c->low - 1) >> 31;
135
136 c->low -= c->range & one_mask;
137 c->range += (range1 - c->range) & one_mask;
138
139 *state = c->zero_state[(*state) + (256 & one_mask)];
140 }
141 refill(c);
142
143 return one_mask & 1;
144 #endif
145 }
146
147 #endif /* AVCODEC_RANGECODER_H */